San Francisco is home to several respectable arts institutions, from the thoroughly modern SFMOMA to the recently rebuilt De Young, whose burnished copper observation tower rises above the canopy of trees in Golden Gate Park. But there’s no shortage of remarkable works of art just sitting out in the open for your enjoyment, and you’ll be out nothing more than the effort to schlep yourself up to them.

The city’s most recent addition is Shanghai artist Zhang Huan’s massive Three Heads Six Arms (pictured, right; photo by Benjamin Chun). This 15-ton copper sculpture has taken up residence in the plaza directly across from City Hall, symbolically cementing the relationship between San Francisco and Shanghai as sister cities and destinations of cultural renown. Inspired by Tibetan religious sculptures destroyed in the Cultural Revolution, Zhang’s aggregation of heads and extremities speaks to the reconstitution of a broken culture, and seems to use the strength of its newly found arms to lift itself up, reaching for something just out of touch.

In nearby Hayes Valley is Patricia’s Green. Once a freeway off-ramp, this stretch of parkland in the center of Octavia Boulevard has become a rotating gallery of public art. Currently standing in its midst (through June 18, 2010) is Ecstasy, a towering female figure made of salvaged and recycled steel. As she stands with her back arched and her face to the sky, her long, luxurious locks of oxidized chains cascade from her head. Ecstasy was just one of eight figures in a much larger work that showed at Burning Man in 2008.

On the green belt on the Embarcadero south of the Ferry Building, Claes Oldenburg and Coosje van Bruggen’s Cupid’s Span playfully pokes up out of the green belt. This massive bow and arrow, evoking San Francisco’s notoriety as a city of both romantic and more carnal pursuits, appears to be lodged pointing downward. It’s as if Cupid himself was so stricken by the city’s beauty that he let it fall from his hands. The taut bow mimics the curves and lines of the Bay Bridge behind.

Photo by Tom Bridge

At 555 Mission Street, amidst skyscrapers and suits, a pair of installations help break the tone of seriousness of downtown’s hustle and bustle. Ugo Rondinone‘s Moonrise comprises a series of Tim Burton-esque heads, both ghoulish and gleeful, staring with hollow eyes from chalky white skulls. In the center of the plaza, Jonathan Borofsky‘s Human Structures pops with colorful, pixelated people piled up high. The park makes a lovely place to stop for lunch, but the sculptures positively glow after dark.